This invention pertains to the art of transport refrigeration, and particularly to that aspect related to an arrangement for maintaining circulation of air within a conditioned trailer or like container.
One increasingly popular mode of control for transport refrigeration units is one in which the control not only provides for modulating control such as high and low cooling and heating, but also provides for automatic stopping and starting of the internal combustion engine driving the refrigerant compressor. One known arrangement which includes a stop-start mode of operation is disclosed in U.S. Pat. No. 4,419,866. As is well known in the art, the operation of the engine is stopped when the temperature in the conditioned trailer is in what is commonly called a null band, in which the thermal requirements of the trailer are basically satisfied.
Since typicaly the evaporator fan within the conditioned trailer is driven by power from the engine, when the engine is stopped, air circulation within the trailer from the evaporator fan is also stopped. This lack of air circulation within the trailer can lead to air stratification or pockets of air, or both, where the temperature is well beyond the desired temperature range of the trailer.
The aim of this invention is to provide an arrangement for a transport refrigeration system of the mechanically refrigerated type in which air circulation can be obtained during a null period by taking advantage of the ram air pressure effect created by trailer movement. While the particular arrangement for accomplishing this with the invention with a particular kind of transport refrigeration unit will be later herein developed, it is noted that the general idea of using RAM air pressure to obtain ventilation by causing an interior fan to circulate air is not new. This is evidenced by U.S. Pat. Nos. 682,872; 607,321; 1,935,590; and 1,969,151. However, none of these systems deal with modern, combustion engine driven, transport refrigeration system such as are currently used.